Veiling glare control with luminaires

ABSTRACT

A lighting system for eliminating specular reflection from work areas from impinging upon the eyes of persons in a workroom, such as a classroom and including a luminaire having a light source and a reflector having prisms which act to redirect longitudinal and transverse direct light from the source into lateral angles eliminating both longitudinal and transverse components of downlight on either side of a longitudinal plane through the light source. A work area receiving beams of longitudinal and transverse light at only lateral angles will not reflect light in the longitudinal directions at angles of &#39;&#39;&#39;&#39;veiling glare.&#39;&#39;&#39;&#39; The refractor also provides sides having prisms redirecting light in the beam direction and upwardly to illuminate portions of the ceiling. Finally, a reflector is included which includes portions facing away from a light source so as to reflect as little light as possible upon the refractor.

United States Patet Wince Mar. 7, 1972 [54] VEILING GLARE CONTROL WITH2,3 i;9 9 2 N 2/19 15 ll="i'ancl ..240/93 LUMINAIRES 3,258,590 6/1966Goodbar ..240/ 106 [721V lnventor: Vearl S. Wince, Newark, Ohio PrimaryExaminer-Samuel S. Matthews Assistant Examiner-Richard L. Moses [73]Assrgnee: goxlrophane Company, inc, New York, Atmmey No"e and None [22]Filed: Dec. 11,1969

2 APPL 3 4330 A lighting system for eliminating specular reflection fromwork areas from impinging upon the eyes of persons in a wor- Related US.Application Data kroom, such as a classroom and including a luminairehaving a light source and a reflector having prisms which act toredirect [63] commuatfon'fmpan longitudinal and transverse direct lightfrom the source into 1968 wh'ch a commuatloq lateral angles eliminatingboth longitudinal and transverse 31, 1967, abandoned, Whlch 1S acommuaPoll of components of downlight on either side of a longitudinalplane ,7 y 6, 1965, abandoned, Whlch 1S a through the light source. Awork area receiving beams of lonconunuatlon-m-pafl of 5611 249,747,1311- 7, 1963, gitudinal and transverse light at only lateral angleswill not abandoned. reflect light in the longitudinal directions atangles of veiling glare. The refractor also provides sides having prisms[52] US. Cl ..240/93, 240l51.11, 240/106 redirecting light in the beamdirection and upwardly to illu- [51] Int. Cl. ..F2lv 13/04 rninateportions of the ceiling. Finally, a reflector is included [58] field ofSearch ..240/93, 25, 106, 51.11 which includes portions facing away froma light source so as to reflect as little light as possible upon therefractor. 56 R f 1 e erences (med 16 Claims, 18 Drawing Figures UNITEDSTATES PATENTS PATENTEDMAR 7 I972 3, 647, 148

sum 1 OF 4 TILE- Ea I EAAZ /iCE RNEYS Pmmenm H912 3.647.148

suznunra I ATTORNEYS VEILING GLARE CONTROL WITI-I LUMINAIRES Thisapplication is a continuation-in-part application of pending applicationSer. No. 788,669, filed Oct. 22, 1968 about to become abandoned, whichin turn was a continuation of application Ser. No. 664,890, filed Aug.31, 1967, now abandoned, which in turn was a continuation of applicationSer. No. 453,709, filed May 6, 1965, now abandoned, which in turn was acontinuation-in-part application of application Ser. No. 249,747, filedJan. 7, 1963, now abandoned.

This invention relates to illumination and has specific reference to thesolution of a very commontype of problem involving the proper seeing ofwritten or printed matter. It has particular reference to provision ofillumination to permit the special performance of specific tasks.

A familiar type of desk work involves the viewing of paper on ahorizontal surface such as the desk for the purpose of reading what iswritten or printed thereon and also writing on such horizontallysupported paper. It is known that the significance and ease of readingof matter on paper surfaces depends upon the contrast of one portion ofthe paper to another as it is viewed. The object of illumination is toprovide the greatest contrast possible between portions which areintended to be dark and portions which are intended to be lighter. Thisis accomplished by the viewer in so arranging his work with respect tothe available illumination that he as far as possible sees by means oflight which is diffused from the surface of the paper rather than bylight which is reflected from the surface of the paper in a manneranalogous to reflection from a mirror or a specular surface. This isdifficult to accomplish with the type of illumination now prevailing inthe work spaces such as classrooms, drafting rooms, offices and thelike. The reason for this is that light sources available today passmost of the light in the direction of nadir or not much more than say 45therefrom. If such a light is placed in a position where it casts thecorrect amount of light on the task being performed, a certain amount oflight from the source is reflected to the eye of the observer much as ifthe paper were a mirror. This mirrorlike reflection results in what iscommonly known as veiling glare and is always present if the lightsource is within a certain area overhead from the point at which thepaper is being viewed. The present invention is intended to eliminate toa substantial degree this deficiency in illumination.

It is therefore a primary object of the present invention to giveillumination to a horizontally disposed piece of paper or the like formost advantageous viewing by a person in a position ordinarily assumedin viewing such material.

It is a further object of the present invention to provide adequateillumination which is substantially free from glare without reference tothe position of the person with respect to the source of illumination,but only requiring a specific orientation with respect to theorientation of the illumination source.

Other objects and advantages will become apparent, as this descriptionproceeds, which may be best understood with reference to the appendeddrawings in which:

FIG. I is a perspective view, showing in diagrammatic form the eye of aperson seated at a desk engaged in a task requiring the perusal of asheet of paper or the like lying thereon;

FIG. 2 is a light distribution diagram of a present commonly utilizedillumination for spaces to be illuminated for reading and the like;

FIG. 3 is a polar diagram illustrating reflection from a spot on a pieceof paper resulting from illumination by a single ray oflight;

FIG. 4 is a diagram similar to FIG. 3 illustrating the same kind ofreflection from a spot on a piece of paper having a greater reflectivitythan that illustrated in FIG. 3, that is, a lighter area of the samepiece of paper;

FIG. 5 is a section of a luminaire having a first preferred embodimentin accordance with the present invention, which luminaire providesillumination of the nature contemplated;

FIG. 5A is a partial view of the luminaire shown in FIG. 5 illustratingan alternative form;

FIG. 6 is a partial longitudinal section of the luminaire shown in FIG.5 taken on line 6-6 of FIG. 5;

FIG. 7 is a light distribution diagram illustrating the transversedistribution oflight from the luminaire shown in FIG. 5 and FIG. 6;

FIG. 8 is a similar diagram showing the longitudinal distribution of thelight through a lobe of light shown in FIG. 7 along a centrallongitudinal plane thereof denoted by the dotdash line of FIG. 7;

FIG. 9 is a diagram of the room shown in FIG. 1, taken as a sectionalview on the plane 9999 of FIG. 1;

FIG. 10 is an elevational cross sectional view of a luminaire having asecond preferred embodiment in accordance with the present invention;

FIG. 11 is a longitudinal section of the luminaire refractor shown inFIG. 10 taken on line 1l11 of FIG. 10;

FIG. 12 is a horizontal section of the luminaire refractor shown in FIG.10 taken from axis 12-12 of FIG. 10;

FIG. 13 is a diagrammatic perspective view showing the relationshipbetween the luminaire of FIGS. 11-12 and the oblong light patterns whichit projects on the working surface;

FIG. 14 is a horizontal section similar to that of FIG. 12 through arefractor having a third preferred embodiment in accordance with thepresent invention;

FIG. 15 is a diagrammatic perspective view showing the relationshipbetween a luminaire with the refractor of FIG. 14 and the light patternswhich it projects on the working surface;

FIG. 16 is a light distribution diagram illustrating the trans-,

verse distribution of light from the luminaire shown in FIGS. 10, 11 and12; and

FIG. 17 is a similar diagram showing the longitudinal distribution ofthe light through a lobe of light shown in FIG. 16 along a centrallongitudinal plane thereof denoted by the dotdash line of FIG. 16.

In order to make clear the factors in the present invention, attentionis invited to the showing in FIG. 1. Point E represents the eye of anobserver engaged in work upon a sheet of paper 10 laid upon a desk Letus imagine that the paper 10 is replaced by a mirror. It is readilyapparent that in looking in the mirror the observer will see the ceilingin the rectangle defined by the points l1, l2, l3, and 14. Consequently,if there is a source of illumination anywhere within the rectangle 11-14the illumination would be seen by the observer at Point E reflected inthe mirror on the desk surface. Continuation of the lines between thecorners of the ceiling rectangle and the corners of the mirror meet atan imaginary point V which is beneath the mirror and on the lineextending perpendicularly from the point E through the mirror a distancebelow the mirror equal to the vertical height the point B is above themirror. Thus any illumination which is cast toward the point V is seenby the eye of the observer at E. If now the imaginary mirror is replacedby a piece of paper hearing writing or printing, a somewhat similarphenomenon takes place. Although the observer does not now see a mirrorimage of illumination used in the ceiling within the rectangle 11 to 14,he will see areas of more intense light on the paper which correspond tothe mirror images of the light sources in the ceiling.

In these more intensely illuminated areas the ability to distinguishbetween different tones in the paper is greatly reduced. The reason forthis may be readily understood by reference to FIGS. 3 and 4. Thesefigures are reflection diagrams of small areas of a piece of paperilluminated by a single light ray] in FIG. 3 and a corresponding ray I'in FIG. 4. The ordinarily diffused reflection which is generated bypaper whether printed upon or plain is distributed in intensity in sucha manner that the reflected candle power may be roughly represented as asphere. From these considerations it can be seen that in the figures ifthe eye were placed directly overhead, the maximum illumination contrastwould be observable between the spot of paper shown in FIG. 3, whichrepresents a dark portion of the paper, and the spot shown in FIG. 4,which represents a light portion of the paper. The diagrams are from anactual piece of paper with printing thereon and represent a viewingcontrast about 4 to 1. This diffused reflection is generated by lightpassing into and between the fibers of the substance of the paper and bymultiple reflections between the fibers before the light emerges. Darkareas, or printed spots naturally result in lesser diffuse reflection asthe ink absorbs the light during its passage through the material andupon its reflection from fiber to fiber.

The difference in length between the vertical arrow in FIG. 3 and thatin FIG. 4 is a representation of this. As we said before, thisdifference is what makes the printing readable. In addition to thishowever, there is another type of reflection from practically allsubstances which may be written or printed upon which is attributableonly to reflections from the surface first struck. This reflection isspecular in nature, results in a sharp increase in apparent brightnessof the paper being viewed. If the eye is placed at a position whichwould correspond to a point to which the incident ray I or I would bereflected if the paper were a mirror, this phenomenon becomes apparent.Thus if the eye were placed at a point along lines or 21 in FIGS. 3 and4, there would be plenty of illumination but the viewing contrastbetween the dark spots shown in FIG. 3 and the light spot shown in FIG.4 falls to a value of about 1.5 to I, this ratio, of course, beinggraphically represented by the length of the arrows pointing in thedirection 20 and 21. This loss in contrast renders the task of readingby light which is reflected in this quasi-specular manner difficult.

This type of illumination and resulting viewing glare have been presentin the places which are illuminated by conventional types of luminairesfor such places. The reason for this can be seen in FIG. 2. FIG. 2 is apolar diagram illustrating the candle power distribution from anordinary luminaire. It can be seen that practically all the light fallswithin the zone of 45 from nadir on each side thereof. If such aluminaire is to give adequate illumination it must of course be placedin a position such that the light does not fall at a higher angle than45 from nadir on the object being viewed. Referring to FIG. 1, thismeans that such a luminaire if placed in the room to properly illuminatethe workpiece I0, must be placed within the rectangle II, 12, I3 and 14,with the result, as above explained, that viewing glare would bepresent. It might be possible, in a room such as that illustrated, toplace the luminaire in such a position that such glare does not occurfor a particular location of the work piece, but general overheadillumination permitting a number of work positions must inevitablyproduce glare at a least some positions.

What is proposed is to provide a luminaire which can be placed anywherein the room with relation to the observer without causing such viewingglare. This is accomplished by the provision of the luminaire which hasa light distribution of such a nature that it casts practically noillumination directly downward, its illumination being concentrated asclosely as possible in planes at a definite lateral angle from nadir(FIGS. 13 and 15). In FIG. 7 there is shown a candle distribution curvetaken in a transverse direction, of an elongated luminaire in accordancewith the present invention. From what has been said before it can beseen that if such a luminaire were suspended directly overheadpractically no light from it would reach the paper under it which is indirect contrast to the conventional luminaire the distribution curve ofwhich is shown in FIG. 2. In that construction, the maximum amount ofboth lateral and longitudinal light possible is cast within say 45 ofnadir, as was said before. Of course a luminaire of the invention, withthe distribution of FIG. 7, within the rectangle II to I4 of FIG. I,does not illuminate tasks being perfonned by the observer whose eye isatE but it does illuminate other parts of the room. For the purpose ofilluminating task 10, it would be necessary to provide a luminaire ofthe nature set forth outside of that rectangle in the ceiling, at whichpoint because of the lateral angles of light distribution of both thelateral and longitudinal components of light, it will cause no viewingglare. It is thus necessary'only to place and space luminaires in theceiling so that they provide illumination on whatever work areas are tobe covered with the assurance that even though the entire room beilluminated there will be no reflected glare anywhere provided theobserver is faced in the right direction, that is longitudinally of theaxis of the luminaire. This is perhaps made clearer by the diagram inFIG. 9. In FIG. 9, the observer is supposed to be looking from the pointE at the piece of paper on his desk between 30 and 31. The point Vrepresents the vertical viewing point for the reflection, and it can beseen that unless light strikes the paper at an angle to reach point V,no reflection will occur. Consequently, from the geometry shown, if aluminaire is provided with negligible light emission within the angle0", as shown for luminaires .25 and 26, the luminaire can be placedanywhere and will not emit longitudinally directed light at glare angleswhich would cause viewing glare. The angle a is of course, the sameangle as that defined by points 30, V, and 31.

It will be noted that the emission curve shown in FIG. 7, is similar tothat shown in FIG. 2, in that they both direct little light at highangles, particularly in the zone from 60 to from nadir. This isimportant to prevent direct glare in the observcrs eyes when theobserver is looking in the near horizontal directions.

The difference in approach between the luminaire of the presentinvention and the conventional luminaire can be stated to be that theconventional luminaire is designed to cast light straight down and insuch a manner that the greatest can dle power is distributed over thesurface to be illuminated. This of course means that inasmuch as theshortest distance from the luminaire to the work is along nadir, thelargest amount of light is concentrated at that point and spread aswidely as possible from nadir to cover the maximum area mostefficiently. The principle involved in the present invention is theconcentration of light emission at lateral angles high enough from nadirto prevent specular reflection from a horizontal surface to theobservers eye.

The details of a luminaire having a first preferred embodiment withwhich this is accomplished are shown in FIGS. 5, 5A and 6 which are,respectively, transverse and partial longitudinal sections of theluminaire. The luminaire is composed of a metallic housing 40 supportingareflector 41, a ballast mechanism 42. and a fluorescent tube 43. Therefractor 44, which may be of glass or plastic, is secured to themetallic structure by means of end plates 45. These luminaires areprovided in conventional lengths. It is intended that they are to beinstalled in the space to be illuminated in the manner shown in FIG. 9,that is, with the length of the luminaire axis lying parallel to thedirection in which the user faces. The refractor may have on the outerface of its horizontal surface portion prisms 46, which refract directlight from the source 43 to emerge in the direction of the ray Q8. Aseries of prisms 4 in the inner face of the inclined bottom portionsalso serve to refract light to emerge as typically shown by the ray 5].Cutoff prisms 50 limit the vertical angle of emission of longitudinallytraveling rays.

Optionally the horizontal surface portion of the bottom portion of therefractor may have prisms 46' on the light incident surface with thecutoff prisms 50' extending laterally completely across the lightemergent surface (FIG. 5A

Before proceeding further, from what has been said up to now, it can beseen that the bottom of the refractor emits very little light having atransverse component within the angle a of FIG. 9 because the activesurface of prisms 49 and 46 redirect all longitudinal as well astransverse light from the source substantially entirely into lateralplanes.

On the sides of the refractor internal longitudinal prisms 53 serve tosplit light from the light source. Part of the direct light incident onprisms 53, typically ray 54, is refracted to emerge in a downwarddirection as exemplified by ray 55, and part is directed upwardly toilluminate the ceiling as indicated by ray 56. This effect is obtainedby so proportioning the prisms that an upper surface 57, thereof directslight downwardly while the lower surface thereof 58 directs lightupwardly as along ray 56. It will be appreciated that the external shapechosen for the sides of the luminaire is dictated, to some extent, bythe ratios desired for the widths of the upper surfaces 57, to those ofthe lower surfaces 58, while at the same time having emergent rays takethe proper direction.

A reflector 41 is provided, having preferably a diffused white finishgiving a reflection distribution as shown by the three polar diagrams onthe three different surfaces thereof. As can be seen, the reflector hasa central lower reflecting portion 60, on each side of which there is anupwardly and outwardly sloping surface 61 and finally a horizontallyextending portion 62 on each side of the reflector. The light fromportion 60 of the reflector, in general, behaves in a manner similar tothe light coming directly from the fluorescent tube 43. Because of theinclination on the surface 61, relatively little light reaches thatportion and a relatively small amount is reflected therefrom asindicated by the small polar curve 63. As a result the light whichreaches the bottom of the refractor from surface 61, is kept at aminimum. Thus the typical ray 65, coming from surface 61, and refractedto emerge as 47, is not of great intensity.

The longitudinal distribution of candlepower from the luminaire is thatshown in FIG. 8. This distribution is obtained by means of externalcutoff prisms 68 in a manner well known in the art. This distribution itwill be noted distributes relatively little light between 60 and 90 ofnadir for the purpose which is well understood, of preventing directglare as the observer looks at the light at low angles.

The second and third preferred embodiments are illustrated in FIGS.through 12 and 14. Referring to FIGS. 10-13, this luminaire consists ofa refractor 70, a specular reflector 71 and a housing 72 which allowsspace 73 for housing the ballast equipment (not shown) for operating thelamp 74. The light source 82 in the second and third preferredembodiments is a concentrated source of light i.e., a small intensesource such as a mercury or other metallic vapor lamp. The verticalsidewalls of the refractor element of these second and third embodimentsinclude vertically extending refracting prisms 75 on the light incidentsurface thereof. As can be seen in the detail shown in FIG. 12 theseinterior refracting prisms 75 control the lateral direction of the lightemerging from the refractor 70. The desired light distribution patternfor the first and second preferred embodiments is illustrateddiagrammatically in FIG. 13. To achieve this desired light distributionwith the second preferred embodiment, whereby the individual will havetotally glarefree illumination if he faces in the direction of axis32-32, the light emitted by the luminaire must not be directed by therefractor only in varying lateral directions (sidewall prism structure75) but must also be directed to varying vertical angles. This verticalcontrol is effected by horizontally extending prisms 76 on the lightemergent surface of the sidewalls of the refractor 70. As can be seenfrom the detail in FIG. 10, a part of the light incident thereon (ray87) is reflected by these horizontally extending caladioptric prisms 76to emerge upwardly (ray 87) to illuminate the ceiling and part of thedirect light (ray 88) is refracted to emerge in a downward direction asexemplified by ray 88'. The ratio of the light to be so reflectedupwardly to that which is to so be reflected downwardly is dependentupon the relative effective widths of the upper and lower surfaces 89,90. The external shape chosen for the size of the luminaire is thereforedictated to some extent by the ratio desired.

The bottom portion of the refractor of the second preferred embodimentis illustrated in FIGS. 10 and 12 in which the bottom portion of therefractor has a substantially circular shape and has a panel extendingsubstantially longitudinally (axis 2-2) thereacross. This panel extendstransversely from the center thereof in both directions to the pointwhere the light from the light source 82 incident on the bottomrefractor portion is emitted in beam direction with no deviation asshown by ray 79-79 in FIG. 10. On the light incident surface of thispanel are longitudinal parallel elongated light spreading prisms 77 andcorresponding parallel light depressing prisms tom section of therefractor established by the panel extending thereacross are comprisedof radial prisms 81 on the light incident surface for providing lateralcontrol of the incident light and concentric prisms (FIG. 10) fordepressing the light incident thereon on the light emergent surfacethereof.

It can be seen that the bottom of the refractor emits very little lighthaving a transverse component within the angle a of FIG. 9 because theactive surfaces of prisms 77 and 80 redirect all longitudinal as well astransverse light from the source substantially entirely into lateralplanes. To achieve the desired light distribution pattern as illustratedin FIG. 15, which enables observers to have glarefree illumination whilefacing either axis 33-33 or 32-32, the third preferred embodiment is tobe utilized. As compared to the vertical light incident prismaticstructure 75 on the sidewalls of the refractor 70 in the secondpreferred embodiment whereby incident light is laterally directed in twodirections, the vertical light incident prismatic structure 75' asillustrated in FIG. 14 would laterally direct light in four lateraldirections as shown by the typical rays emergent therefrom. Thehorizontal prisms 76 on the outer surface would control the lightvertically in the same manner as prisms 76 on refractor 70. On thebottom panel, a central portion is comprised of concentric prisms 77' onthe light incident surface thereof to control the light vertically andradial prisms 78 on the light emergent surface to provide for lateralcontrol. The pn'sm structure outside of this circular portion iscomprised of radial prisms 81' on the light incident surface givinglateral control and concentric prisms 80' on the light emergent surfacefor achieving vertical control of the light.

Radial prisms 81 align with the planes in which the light rays in theradiant emission of light from the concentrated source are directed inthe same manner as the longitudinal prisms 49 of the luminaire of FIG. 5aligns with the planes in which the longitudinal components of lightfrom the linear source 43 are directed and act to redirect the lightonto work areas W, X, Y and Z (FIG. 15). Prisms 81 lying generally alongand on either side of axes 32-32 and 33-33 act to lift the longitudinalcomponents of light from the source onto the work areas on either sideof each axis to eliminate glare along the axes and veiling glare fromthe work surfaces in accordance with the object of the invention. 7

It can be appreciated that to uniformly illuminate the entire worksurface, the luminaires of the present invention would have to have thesizes of the individually illuminated sections so designed that by aproper placement of a plurality of these luminaires all light would beincident so as to provide glarefree viewing and at the same time totaluniform illumination of a complete work surface would be achieved.

To obtain even illumination of the floor surface it is obvious from anexamination of FIG. 15 that the adjacent luminaire shown in FIGv 14should be spaced apart approximately onehalf the mounting height abovethe work plane in both directions 32-32 and 33-33. The luminaire shownin FIGS. l0, l1 and 12 should be spaced apart in the direction 32-32approximately the distance of the mounting height while at right anglesto this direction they must be spaced apart onehalf the mounting height.

The operation of the luminaire should now be clear. It can best bevisualized by considering that the primary function of the reflector andrefractor is to cause emergent light, not so much to strike a particularregion in relation to the lamp, but to strike the surface to be viewedat a particular angle. If the viewer is faced in the direction of thelength of the luminaire, he finds that little light from the portion ofthe luminaire forward of him (within the ceiling rectangle mentioned),reaches the surface he is viewing. Illumination must, therefore, comefrom luminaires elsewhere in the ceiling. These luminaires, of course,cannot cause glare because of their position.

A typical glare producing ray has a component in a longitudinaldirection toward the viewer, and a component from nadir in a transversedirection less than one-half of the angle subtended by the viewedsurface. Both components must be present. By providing a luminaire whichcasts very little light having a transverse component within that angleto nadir, viewing glare is substantially eliminated.

It is to be understood that variations in the construction of thetypical luminaire shown in the present description can be made withoutdeparting from the invention, the scope of which is best understood bythe appended claims.

What I claim is:

1. in combination: a substantially horizontally disposed work surface tobe viewed by a person facing the same and a luminaire arranged above andlaterally of said work surface said luminaire including a linear lightsource having an horizontal axis extending in the direction said surfaceis to be viewed and also including an elongated refractor, saidrefractor having light incident and emergent surfaces, said incidentsurface having continuous linear prisms extending beneath said lightsource and parallel to said axis and having active surfaces constitutingmeans for receiving incident light from the linear light source and forredirecting light rays emitted by said light source and incident uponsaid active surfaces substantially entirely into relatively narrowangular ranges on opposite sides of and remote from a vertical planethroughand parallel to the axis of the linear light source and furtherconstituting means for directing the emitted light onto said worksurface at such lateral and longitudinal angles for preventingreflection from the horizontally disposed work surface into the personseye, said refractor further including prismatic cutoff means forlimiting the vertical angle of light emission.

2. An elongated luminaire for illuminating horizontal surfaces with aminimum of viewing glare in the longitudinal direction of the luminaire,comprising: a linear light source, an elongated refractor having abottom panel and side panels on opposite sides of said bottom panel,said panels having light incident and emergent surfaces, the lightincident surface of said bottom panel having first linear prismsextending beneath and substantially parallel to said linear light sourceand having active surfaces constituting means for redirectingsubstantially all longitudinal and substantially all lateral light raysemitted by said light source and incident upon said active surfacessubstantially entirely away from a vertical plane through and parallelto the axis of the linear light source into an angular range from 30 to60 from said vertical plane on opposite sides thereof and onto thehorizontal surfaces at angles for preventing reflection therefrom toviewers looking at the surfaces in longitudinal directions, said sidepanels respectively having second linear prisms extending parallel tosaid linear light source, said second linear prisms having surface meansdisposed for redirecting substantially all longitudinal and laterallight rays emitted by the light source and incident thereonsubstantially parallel to the light emergent from that part of thebottom panel which is adjacent to the respective side panel, saidrefractor including prismatic cutoff means along said bottom panel forlimiting the vertical angle of emission of longitudinally travellingrays.

3. A luminaire according to claim 1, wherein said prismatic cutoff meansare provided on the outside of the refractor and constitute transverselyextending prisms for limiting the emission of light below approximately60 from nadir in the longitudinal direction of the refractor.

4. A luminaire according to claim 2, which includes a reflector arrangedabove said light source and having a horizontal center portion, inclinedportions respectively connected to opposite sides of said centerportion, and side portions respectively connected to said inclinedportions, said inclined portions generally facing away from said lightsource and such that only a relatively small amount of light from saidlight source is reflected by said inclined portions to said first andsecond linear prisms.

5. A luminaire according to claim 2, in which the second linear prismshave further surfaces constituting means for redirecting light from saidlight source, and incident thereupon, upwardly for illuminating asurface above the luminaire.

6. A lighting system for illuminating a plurality of laterally andlongitudinally spaced work areas spaced from ground level and to beviewed in the longitudinal direction, said system comprising a pluralityof longitudinally extending luminaires, some of which are disposeddirectly above respective ones of said work areas and constituting meansfor substantially distributing longitudinal and transverse components oflight at only lateral angles for illuminating work areas spacedlaterally of said respective work areas, said luminaires furtherconstituting means for substantially eliminating transverse componentsof light including rays extending longitudinally along a longitudinalcenter plane through the luminaire and within a range of from 0 toapproximately 30 on either side thereof, said last-named means alsoconstituting means for reducing indirect veiling glare from said workareas in predetermined longitudinal directions; each of said lurninairesincluding preferably one linear light source having an axis extendingparallel to the longitudinal direction, and also including an elongatedrefractor having linear prisms extending beneath and parallel to saidaxis and having active surfaces on its light incident surfaceconstituting means for redirecting substantially all longitudinal andtransverse light'rays from said light source and incident upon saidactive surfaces into lateral planes within an angular range of from 30to approximately 60 on opposite sides of and remote from thelongitudinal center plane through the luminaire, said refractorincluding prismatic cutoff means for limiting the vertical angle oflightemission.

7. The combination according to claim 4, in which said reflectorincludes surface means for diffusing light incident thereon whereby thelight reflected to said refractor bottom panel is diffused light.

8. in combination: a substantially horizontally disposed work surface tobe viewed by a person facing the same, and a luminaire arranged aboveand laterally of said work surface, said luminaire including aconcentrated light source and a refractor, said refractor having abottom portion below said light source and including prismatic means onit light incident surface for receiving incident light from said lightsource and for redirecting substantially all light rays emitted by saidlight source and incident thereon into lateral planes within arelatively narrow angular range on opposite sides of and remote from aopen vertical plane through said light source and parallel to thedirection in which said surface is to be viewed and for directing theemitted light onto to said work surface at such lateral and longitudinalangles for preventing reflection from the horizontally disposed worksurface into the person s eyes.

9. The combination as defined in claim 8 wherein said refractor hasbottom and side portions, said bottom portion including a panelextending substantially thereacross, said panel being bisected by avertical plane passing through said light source, said panel having alight incident and a light emergent surface, said prismatic meanscomprising a plurality of elongated prisms on said light incidentsurface extending parallel to said plane for spreading light incidentthereon, and a plurality of transverse elongated prism means on saidlight emergent surface for depressing light incident thereon.

10. The combination as defined in claim 8 wherein said refractorincludes side portions extending upwardly from said bottom portion andsaid side portions include prismatic means for distributing the lightfrom said source into four spaced work surfaces, and said firstmentioned prismatic means also comprising means for distributing thelight into said four spaced work surfaces.

11. The combination as defined in claim 10, wherein said bottom portionhas a substantially circular shape, and said first mention ed prismaticmeans comprises a central circular portion having concentric prismaticmeans on the light incident surface thereof for vertically controllingsaid incident light and having radial prismatic means on the lightemergent surface for laterally controlling said light.

E2. in a luminaire for disposition above and laterally of a worksurface, the luminaire including a light source and a refractor, saidrefractor having light incident and light emergent surfaces, said lightincident surface having continuous prisms extending below the lightsource and for extending in planes laterally of the horizontal surface,and having active surfaces constituting means for receiving incidentlight rays from the light source and for redirecting substantially alllight rays emitted longitudinally and transversely relative to theactive surfaces substantially entirely into lateral planes within arelatively narrow angular range on opposite side of an remote from avertical plane through the light source and for directing the emittedlight onto the work surface at such relative lateral and longitudinalangles thereto for preventing reflection from the horizontally disposedwork surface into the persons eye, said refractor including prismaticmeans for effecting a predetermined vertical angle of emission of thelight directed by said first mentioned prisms.

13. The combination according to claim 12, wherein said light source isa linear light source having an axis extending parallel to saidhorizontal surface, said refractor being elongated, said prisms on thelight incident surface of said refractor being linear and extendingparallel to the axis of said light source and wherein said center planeextends in a direction parallel to the axis of the light source.

14. In combination: a substantially horizontally disposed work surfaceto be viewed by a person facing the same, and a luminaire arranged aboveand laterally of said work surface said luminaire including a lightsource and a refractor, said refractor having light incident andemergent surfaces, said incident surface having continuous prismsextending below said light source and in planes laterally of saidhorizontal surface, and having active surfaces constituting means forreceiving light from the light source and for redirecting substantiallyall longitudinal and transverse light rays emitted by said light sourceand incident upon said active surfaces substantially entirely intolateral planes within a relatively narrow angular range on oppositesides of and remote from a vertical plane through the light source andparallel to the direction in which said surface is to be viewed and forredirecting the emitted light onto said work surface at such lateral andlongitudinal angles for preventing reflection from the horizontallydisposed ill) work surface into the person's eye, said refractorincluding prismatic means for effecting a predetermined vertical angleof emission of the light redirected by said first-mentioned prisms.

15. The combination according to claim 14, wherein said light source isa linear light source having an axis extending parallel to saidhorizontal surface, said refractor being elongated, said prisms on thelight incident surface of said refractor being linear and extendingparallel to the axis of said light source and wherein said center planeextends in a direction parallel to the axis of the light source.

16. In combination: a substantially horizontally disposed work surfaceto be viewed by a person facing the same, and a luminaire arranged aboveand laterally of said work surface, said luminaire including aconcentrated light source and a refractor, said refractor having abottom portion below said light source and including on its lightincident surface prismatic means for receiving light from said lightsource and for redirecting substantially all light rays emitted by saidlight source and incident thereon into lateral planes within arelatively narrow angular range on opposite sides of and remote from avertical plane through said light source and parallel to the directionin which said work surface is to be viewed and for directing the emittedlight onto said work surface at such lateral and longitudinal angles forpreventing reflection from the horizontally disposed work surface intothe person's eyes, said refractor including side portions extendingupwardly from said bottom portion and said side portions including ontheir light incident surfaces prismatic means for distributing the lightfrom said source into four spaced work surfaces, said first mentionedprismatic means also comprising means for distributing the light intosaid four spaced work surfaces, said bottom portion further including aring shaped portion surrounding a circular portion and having radialprismatic means on the light incident surface for laterally controllingthe incident light and concentric prismatic means on said light emergentsurface for vertically controlling said light, said last mentionedradial and concentric prismatic means also constituting means fordistributing light onto said four work surfaces.

1. In combination: a substantially horizontally disposed work surface tobe viewed by a person facing the same and a luminaire arranged above andlaterally of said work surface said luminaire including a linear lightsource having an horizontal axis extending in the direction said surfaceis to be viewed and also including an elongated refractor, saidrefractor having light incident and emergent surfaces, said incidentsurface having continuous linear prisms extending beneath said lightsource and parallel to said axis and having active surfaces constitutingmeans for receiving incident light from the linear light source and forredirecting light rays emitted by said light source and incident uponsaid active surfaces substantially entirely into relatively narrowangular ranges on opposite sides of and remote from a vertical planethrough and parallel to the axis of the linear light source and furtherconstituting means for directing the emitted light onto said worksurface at such lateral and longitudinal angles for preventingreflection from the horizontally disposed work surface into theperson''s eye, said refractor further including prismatic cutoff meansfor limiting the vertical angle of light emission.
 2. An elongatedluminaire for illuminating horizontal surfaces with a minimum of viewingglare in the longitudinal direction of the luminaire, comprising: alinear light source, an elongated refractor having a bottom panel andside panels on opposite sides of said bottom panel, said panels havinglight incident and emergent surfaces, the light incident surface of saidbottom panel having first linear prisms extending beneath andsubstantially parallel to said linear light source and having activesurfaces constituting means for redirecting substantially alllongitudinal and substantially all lateral light rays emitted by saidlight source and incident upon said active surfaces substantiallyentirely away from a vertical plane through and parallel to the axis ofthe linear light source into an angular range from 30* to 60* from saidvertical plane on opposite sides thereof and onto the horizontalsurfaces at angles for preventing reflection therefrom to viewerslooking at the surfaces in longitudinal directions, said side panelsrespectively having second linear prisms extending parallel to saidlinear light source, said second linear prisms having surface meansdisposed for redirecting substantially all longitudinal and laterallight rays emitted by the light source and incident thereonsubstantially parallel to the light emergent from that part of thebottom panel which is adjacent to the respective side panel, saidrefractor including prismatic cutoff means along said bottom panel forlimiting the vertical angle of emission of longitudinally travellingrays.
 3. A luminaire according to claim 1, wherein said prismatic cutoffmeans are provided on the outside of the refractor and constitutetransversely extending prisms for limiting the emission of light belowapproximately 60* from nadir in the longitudinal direction of therefractor.
 4. A luminaire according to claim 2, which includes areflector arranged above said light source and having a horizontalcenter portion, inclined portions respectively connected to oppositesides of said center portion, and side portions respectively connectedto said inclined portions, said inclined portions generally facing awayfrom said light source and such that only a relatively small amount oflight from said lighT source is reflected by said inclined portions tosaid first and second linear prisms.
 5. A luminaire according to claim2, in which the second linear prisms have further surfaces constitutingmeans for redirecting light from said light source, and incidentthereupon, upwardly for illuminating a surface above the luminaire.
 6. Alighting system for illuminating a plurality of laterally andlongitudinally spaced work areas spaced from ground level and to beviewed in the longitudinal direction, said system comprising a pluralityof longitudinally extending luminaires, some of which are disposeddirectly above respective ones of said work areas and constituting meansfor substantially distributing longitudinal and transverse components oflight at only lateral angles for illuminating work areas spacedlaterally of said respective work areas, said luminaires furtherconstituting means for substantially eliminating transverse componentsof light including rays extending longitudinally along a longitudinalcenter plane through the luminaire and within a range of from 0* toapproximately 30* on either side thereof, said last-named means alsoconstituting means for reducing indirect veiling glare from said workareas in predetermined longitudinal directions; each of said luminairesincluding preferably one linear light source having an axis extendingparallel to the longitudinal direction, and also including an elongatedrefractor having linear prisms extending beneath and parallel to saidaxis and having active surfaces on its light incident surfaceconstituting means for redirecting substantially all longitudinal andtransverse light rays from said light source and incident upon saidactive surfaces into lateral planes within an angular range of from 30*to approximately 60* on opposite sides of and remote from thelongitudinal center plane through the luminaire, said refractorincluding prismatic cutoff means for limiting the vertical angle oflight emission.
 7. The combination according to claim 4, in which saidreflector includes surface means for diffusing light incident thereonwhereby the light reflected to said refractor bottom panel is diffusedlight.
 8. In combination: a substantially horizontally disposed worksurface to be viewed by a person facing the same, and a luminairearranged above and laterally of said work surface, said luminaireincluding a concentrated light source and a refractor, said refractorhaving a bottom portion below said light source and including prismaticmeans on it light incident surface for receiving incident light fromsaid light source and for redirecting substantially all light raysemitted by said light source and incident thereon into lateral planeswithin a relatively narrow angular range on opposite sides of and remotefrom a open vertical plane through said light source and parallel to thedirection in which said surface is to be viewed and for directing theemitted light onto to said work surface at such lateral and longitudinalangles for preventing reflection from the horizontally disposed worksurface into the person''s eyes.
 9. The combination as defined in claim8 wherein said refractor has bottom and side portions, said bottomportion including a panel extending substantially thereacross, saidpanel being bisected by a vertical plane passing through said lightsource, said panel having a light incident and a light emergent surface,said prismatic means comprising a plurality of elongated prisms on saidlight incident surface extending parallel to said plane for spreadinglight incident thereon, and a plurality of transverse elongated prismmeans on said light emergent surface for depressing light incidentthereon.
 10. The combination as defined in claim 8 wherein saidrefractor includes side portions extending upwardly from said bottomportion and said side portions include prismatic means for distributingthe light from said source into four spaced work surfaces, aNd saidfirst mentioned prismatic means also comprising means for distributingthe light into said four spaced work surfaces.
 11. The combination asdefined in claim 10, wherein said bottom portion has a substantiallycircular shape, and said first mentioned prismatic means comprises acentral circular portion having concentric prismatic means on the lightincident surface thereof for vertically controlling said incident lightand having radial prismatic means on the light emergent surface forlaterally controlling said light.
 12. In a luminaire for dispositionabove and laterally of a work surface, the luminaire including a lightsource and a refractor, said refractor having light incident and lightemergent surfaces, said light incident surface having continuous prismsextending below the light source and for extending in planes laterallyof the horizontal surface, and having active surfaces constituting meansfor receiving incident light rays from the light source and forredirecting substantially all light rays emitted longitudinally andtransversely relative to the active surfaces substantially entirely intolateral planes within a relatively narrow angular range on opposite sideof an remote from a vertical plane through the light source and fordirecting the emitted light onto the work surface at such relativelateral and longitudinal angles thereto for preventing reflection fromthe horizontally disposed work surface into the person''s eye, saidrefractor including prismatic means for effecting a predeterminedvertical angle of emission of the light directed by said first mentionedprisms.
 13. The combination according to claim 12, wherein said lightsource is a linear light source having an axis extending parallel tosaid horizontal surface, said refractor being elongated, said prisms onthe light incident surface of said refractor being linear and extendingparallel to the axis of said light source and wherein said center planeextends in a direction parallel to the axis of the light source.
 14. Incombination: a substantially horizontally disposed work surface to beviewed by a person facing the same, and a luminaire arranged above andlaterally of said work surface said luminaire including a light sourceand a refractor, said refractor having light incident and emergentsurfaces, said incident surface having continuous prisms extending belowsaid light source and in planes laterally of said horizontal surface,and having active surfaces constituting means for receiving light fromthe light source and for redirecting substantially all longitudinal andtransverse light rays emitted by said light source and incident uponsaid active surfaces substantially entirely into lateral planes within arelatively narrow angular range on opposite sides of and remote from avertical plane through the light source and parallel to the direction inwhich said surface is to be viewed and for redirecting the emitted lightonto said work surface at such lateral and longitudinal angles forpreventing reflection from the horizontally disposed work surface intothe person''s eye, said refractor including prismatic means foreffecting a predetermined vertical angle of emission of the lightredirected by said first-mentioned prisms.
 15. The combination accordingto claim 14, wherein said light source is a linear light source havingan axis extending parallel to said horizontal surface, said refractorbeing elongated, said prisms on the light incident surface of saidrefractor being linear and extending parallel to the axis of said lightsource and wherein said center plane extends in a direction parallel tothe axis of the light source.
 16. In combination: a substantiallyhorizontally disposed work surface to be viewed by a person facing thesame, and a luminaire arranged above and laterally of said work surface,said luminaire including a concentrated light source and a refractor,said refractor having a bottom portion below said light source andincluding on iTs light incident surface prismatic means for receivinglight from said light source and for redirecting substantially all lightrays emitted by said light source and incident thereon into lateralplanes within a relatively narrow angular range on opposite sides of andremote from a vertical plane through said light source and parallel tothe direction in which said work surface is to be viewed and fordirecting the emitted light onto said work surface at such lateral andlongitudinal angles for preventing reflection from the horizontallydisposed work surface into the person''s eyes, said refractor includingside portions extending upwardly from said bottom portion and said sideportions including on their light incident surfaces prismatic means fordistributing the light from said source into four spaced work surfaces,said first mentioned prismatic means also comprising means fordistributing the light into said four spaced work surfaces, said bottomportion further including a ring shaped portion surrounding a circularportion and having radial prismatic means on the light incident surfacefor laterally controlling the incident light and concentric prismaticmeans on said light emergent surface for vertically controlling saidlight, said last mentioned radial and concentric prismatic means alsoconstituting means for distributing light onto said four work surfaces.